I just put Adjustable Halo's on my rig and as mentioned in the instructions if you run into cavitation raise the pick ups by 1/8" at a time untill it stops. Mine are adjustable with set screws I don't know if you can do that with other applications however.

Originally posted by NEXTASEX current won't affect gps readings. You should rethink that statement.

yes it will, GPS measures your speed by FIXing on at least 3 sats
some Gps will work with 2, but will not be very accurate. The more the better , if the current is moving 4 mph and you drive with it , you will appear to be going faster , but in reality you are
not. for a accurate reading a Still lake will be your best move
and lock on many Sats.